Variables in Java: Primitive Data Types vs Reference or Non-Primitive Types

Variables in Java are used to hold a certain value. They are declared as a variable type and are given a name. Then they are assigned a value which is then stored in a memory location.

Primitive Variables

There are eight different types of primitive variables in Java. They hold different data types and are allocated a pre-defined spaced in the memory.

Data Type	Size	Minimum	Maximum	Default
boolean	1 bit			false
char	2 bytes			‘\u0000\
byte	1 byte	-128	127	0
short	2 bytes	-32,768	32,768	0
int	4 bytes	-2,147,483,648	2,147,483,647	0
long	8 bytes	-9.22337E+18	9.22337E+18	0
float	4 bytes			0.0f
double	8 bytes			0.0d

 

You can set values as:

byte b = 1;
short s = 20;
int i = 20,000;
long l = 200L;
float f = 100.2f;
double d = 100.2d;
char c = ‘a’;

Note how double and float values are declared so that the compiler knows what type of data type they are. They are known as literals.

Non-Primitive or Reference Variables

These are data types that are pre-defined objects in java or are created by the user as an object. They must be defined and initiated to be used. For example: String, Array, enum, interface and user-defined class.

Using Strings

char[] characArray = {'K', 'a', 't', 'h', 'm', 'a', 'n', 'd', 'u'};
String placeName = new String(characArray);
System.out.println(placeName);

Output

Kathmandu

There’s a lot more that you can do with strings with helper classes and methods like concatenating, comparing etc.